Storage device manufacturers typically test manufactured storage devices for compliance with a collection of requirements. Test equipment and techniques exist for testing large numbers of storage devices serially or in parallel. Manufacturers tend to test large numbers of storage devices simultaneously. Storage device testing systems typically include one or more racks having multiple test slots that receive storage devices for testing.
During the manufacture of disk drives or other storage devices, it is common to control the temperature of the storage devices, e.g., to ensure that the storage devices are functional over a predetermined temperature range. For this reason, the testing environment immediately around the storage devices can be varied under program control. In some known testing systems, sometimes called “batch testers,” the temperature of plural storage devices is adjusted by using cooling or heating air which is common to all of the storage devices.
Batch testers generally require all storage device tests to be at substantially the same temperature, and require all storage devices to be inserted or removed from the test system at substantially the same time. Storage devices generally vary substantially in both the time required to test them and the amount of time that each test requires a particular ambient temperature. Because of these variations, batch testers tend to inefficiently use available testing capacity. There are also known testing systems that allow separate control of the insertion, removal, and temperature of each storage device. These test systems tend to more efficiently use the available testing capacity, but require duplication of temperature control components across every test slot, or sharing of those components among a small number of test slots.
Some storage device test systems use heated or cooled air to heat or cool the storage device. For separate thermal control of each storage device, a separate closed-loop air flow is sometimes used, with heaters or coolers disposed in the air flow. In some examples, the storage device is allowed to self-heat, and thus only a cooler is used. Heating may also be enhanced by reducing or otherwise controlling the flow of the air, and cooling may also be enhanced by increasing the air flow. In some examples of separate thermal control of each storage device, air is drawn from ambient air outside of the tester, rather than through a cooler that draws heat from a closed loop air flow.
Disadvantages of systems with separate thermal controls for each test slot include the need for many separate thermal control components for each test slot (e.g., heaters, coolers, fans, and/or controllable baffles). In addition, efficient use of energy generally requires each test slot to have a closed loop air flow system during at least some of the operating time. A closed loop air flow system typically requires ducting for the air to flow in both directions, to complete a loop, which requires additional space for the air return path. In addition, coolers may create condensation when operating below the dew point of the air. The formation of condensation may be avoided at the cost of reduced cooling performance, by limiting the coolant temperature. Alternatively, the formation of condensation may be avoided controlling and/or removing the moisture content in the air.